1. Field of the Invention
The present invention relates to a resist processing system, and a resist processing method.
2. Description of the Related Art
For example, in a photolithography step of a process of manufacturing a semiconductor device, a coating-development-exposure system is used. The coating-development-exposure system includes a coating-development unit for forming a resist film by applying a resist on the surface of a semiconductor wafer and for developing the resist film, and an exposure unit for carrying out an exposure process on the resist film. The coating-development unit has an interface for loading/unloading wafers between the exposure unit and itself.
In the interface, the wafers exposed by the exposure unit are received by the first carrying means and passed to the second carrying means which are provided in the coating-development unit. Then, the second carrying means carries the wafers to each of the processing devices. For example, the second carrying means carries the wafers to an oven provided in the coating-development unit. In this oven, the wafers are subjected to a post exposure baking (PEB) process. After the PEB process is completed, the wafers are carried to a cooling device. In this cooling device, the wafers are cooled. After the cooling, the wafers are carried by the second carrying means to each of the processing devices, where further necessary processes are carried out on the wafers successively, such as a development process.
In a conventional coating-development-exposure system, for the purpose of improving the throughput, the second carrying means provided in the coating-development unit moves at all times between the processing units including the interface, the oven and the cooling device, so that the wafers are continuously carried between the processing units. In order to further improve the throughput, it is preferable that the wait time, that is the time period from when the second carrying means arrives at the interface or each of the processing devices of the coating-development processing unit, to when the loading/unloading of wafers is started, should be shortened as much as possible. In the conventional coating-development-exposure system, an operation timing of the second carrying means is set in advance on the basis of time set for each one of the procedures carried out by the exposure unit and the coating-development unit.
However, in some cases, the exposure unit requires a more time than the predetermined set time required for the exposure unit. More specifically, in the case where the alignment of a wafer is not accurately completed in one time for some reason and the alignment must be carried out two times or more, or where the projection exposure time is prolonged due to a decrease in the light intensity of the light source, the operation time required in the exposure unit is prolonged.
As described above, in the conventional coating-development-exposure system, the operation timing of the second carrying means in the coating-development unit is set on the basis of the predetermined set time required for the exposure unit. Therefore, in the case where the actual time required for the exposure unit is longer than the preset time, a wafer is not present at the interface at the preset timing. Regardless of whether or not a wafer is present, the second carrying means operates in the preset timing and carries out the operation of receiving a wafer when arrives at the interface. Then, the second carrying means moves on to the oven without receiving a wafer. In a normal operation at the oven, the second carrying means unloads a wafer which has been subjected to the PEB process, and load a not-yet-processed wafer. However, even in the case where the second carrying means receives no wafer which has been exposed, the means carries out the operation of carrying a wafer into the oven, without a wafer. As described above, the second carrying means, without having a wafer, carries out a wafer carrying operation consecutively between the processing devices such as the oven and the cooling device provided in the coating-development unit. As a result, the throughput of the resist process in the coating-development-exposure system is extremely decreased.
In the interface, a wafer which is received from the exposure unit later than the preset timing, must wait the second carrying means to come around and back there again, at a wafer loading/unloading position of the interface, where wafers are loaded/unloaded to/from the second carrying means. If there is a long time elapse between the wafer exposure process and the PEB process, the line width of the resist pattern which has been subjected to the exposure changes in the time elapse when the resist material is a chemical amplification type. Therefore, it may not be possible to obtain a desired width of a resist pattern.